摘要:
松嫩地块位于兴蒙造山带东部, 其内及周边地区早前寒武纪的岩石记录报道极少.笔者对黑龙江省龙江县大泉子屯碎裂岩化花岗岩进行年代学和地球化学研究表明, 该岩石的锆石LA ICP MS U-Pb年龄为(2579±15) Ma(n=20, MSWD=0.49), 代表了花岗岩的结晶年龄, 为新太古代晚期, 地球化学特征显示该花岗岩为富钠花岗岩, 具TTG中奥长花岗岩特征.本套新太古代花岗岩为松嫩地块及其周边地区的首次报道,证实了龙江地区存在早前寒武纪地质记录, 为本区新太古代TTG岩石组合的寻找提供依据, 也说明松嫩地块及其周边地区不仅存在古元古代岩浆活动记录、也存在新太古代岩浆活动记录, 同时为松嫩地块及其周边大量的新太古代岩浆成因碎屑锆石的来源研究提供依据, 为兴蒙造山带中残留的早期地质记录研究及兴蒙造山带的构造格局划分提供新材料.
Abstract:
Reports about Early Precambrian rocks in Songnen Massif and its surrounding areas located in the eastern Xing–Meng Orogenic Belt are very insufficient. In this paper, the authors studied geochronology and geochemistry of cataclasitic granite from Daquanzi Village in Longjiang Coutry, Heilongjiang Province. The results show that the granite, having a concordia 207Pb/206Pb age of (2 579±15) Ma (n=20, MSWD=0.49) determined by zircon LA ICP MS U-Pb method, was crystallized in Late Neoarchean, thus belonging to soda-rich granite with the characteristics of trondhjemite, TTG. The discovery of Neoarchean granite is the first report in Songnen massif and its surrounding areas, which confirms that early Precambrian geological record exists in Longjiang area, thus contributing to the search for Neoarchean TTG. This discovery indicates that, in Songnen massif and its surrounding areas, there existed Neoarchean magmatic activity not merely in Paleoproterozoic, thus providing a basis for source of large quantities of Neoarchean detrital orginal zircons. This study provides new materials for the researches on remaining early geological records and geotectonic framework of Xing-Meng orogenic belt.
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